USNI News got the scoop on the previously unannounced tests, citing anonymous sources, but did not say specifically when the test firing had occurred or if the experiments had successfully fulfilled all of the test points. RIMPAC 2018, which occurred in the Pacific Ocean off the coast of the Hawaiian island of Kauai, ran from June 27 to Aug. 2, 2018.

Despite the test being unclassified, according to USNI News, the Navy has refused to confirm or deny it occurred at all. It is increasingly apparent that the service has something of a gag order, formal or not, on public discussions about the HVP, as well as its Electromagnetic Railgun (EMRG) program. Originally intended for the railgun specifically, the HVP, sometimes referred to now as the Gun Launched Guided Projectile (GLGP), has since evolved its own effort to develop a high-speed, multi-purpose projectile that will also work in traditional naval guns and land-based howitzers that use powder as a propellant. BAE Systems is the lead contractor on both projects.

Joseph Trevithick

Mockups of the HVP for use in various different weapons. The five-inch type is at the top.

In January 2018, Vincent Sabio, the individual then in charge of the Hypervelocity Gun Weapon System (HGWS) program, an effort related to the HVP within the Pentagon’s secretive Strategic Capabilities Office (SCO), seemed to imply there would be a test involving the projectiles before the end of the year. “My program ends less than a year from now,” Sabio told a gathering at the Center for Strategic and International Studies think tank in Washington, D.C.

In 2016, SCO conducted separate tests of the HVP using unspecified conventional weapons, but it's not clear if those experiments occurred on land or at sea. SCO worked together with the Navy for the subsequent tests in the Pacific, according to USNI News.

The Navy wants to be able to shoot the HVPs at velocities up to Mach 3 from the Mk 45s using traditional propellant charges. This is half as fast as the service has been able to send the projectiles flying from its prototype railguns, but is still significantly faster than the speed of traditional five-inch shells.

With a maximum range close to 50 miles, the HVPs also dramatically outrange existing ammunition and can quickly cover that greater distance. This makes the rounds well suited to time-sensitive strikes against targets ashore. That speed and range would allow them to more quickly engage other warships and even fast-moving smaller watercraft, too. This would improve the Mk 45’s anti-surface warfare capabilities and give it a secondary close-in defense role against swarming boats.

The Navy hopes that the speed of the new projectiles will also give the Mk 45 much more robust anti-aircraft and all-new anti-missile capabilities, as well. At present, the service’s various warships rely on a mix of surface-to-air missiles and close-in defense systems to defend against those threats.

USN

A graphic showing the various possible roles for HVP-armed ships, as well as those equipped with railguns.

The problem is that weapons such the Evolved Sea Sparrow Missile (ESSM) and the Standard Missile-2 (SM-2) are expensive per-shot especially for taking down small drones or incoming missiles. Close-in systems, including the Rolling Airframe Missile (RAM) and Phalanx Close-In Weapon System (CIWS), are true to their name and only provide a last line of defense against air and missile threats.

“That [hyper velocity] projectile has been independently costed – not by me, I wouldn’t expect you to believe my costing – but … by Navy IWS [Program Executive Office Integrated Warfare Systems] at about $85,000 a round,” SCO’s Sabio said in January 2018. “You can shoot a lot of those things and not feel badly about it.”

For comparison, each of the latest Block II ESSMs costs the Navy around $2 million, while individual RAMs set the service back around $640,000 apiece. The new gun-launched projectile’s $85,000 price tag is more than three times higher than the initial estimates, but is still exponentially cheaper than these missiles.

The Mk 45 also has the benefits of significant magazine depth and a relatively high rate of fire for a naval gun. Arleigh Burkes can carry around 600 shells for the guns, which can pump out shells at between 16 and 20 rounds per minute. This also means the gun could rapidly shoot multiple rounds to impact nearly simultaneously over a larger area.

The HVP’s cost could still grow in the future as the Navy continues to explore exactly what guidance options it might want to use to improve the projectile’s capabilities against different target sets and reduce its vulnerability to jamming, spoofing, and other countermeasures. Air and missile defense-focused subvariants would also need to be more maneuverable than surface strike types.

We don’t know the exact HVP configuration the Navy tested during RIMPAC 2018. But even at $100,000 per shell, it would still be a tenth of the price of a Rolling Airframe Missile and even cheaper than more advanced types.

The fast-flying projectile’s capabilities and price also make it attractive as an option for the Zumwalt-class stealth destroyer’s 155mm main guns. The weapons have been dead weight on those ships since the Navy canceled its plans to purchase the guided Long-Range Land Attack Projectile (LRLAP) after its price point grew to whopping $800,000 per shell.

If everything goes according to plan now, the HVP will work with Mk 45 guns, the 155mm guns on the Zumwalts, as well as 155mm howitzers on land and railguns the U.S. Army and Navy are testing separately. This will also help keep development and procurement costs low, since the main difference between the ammunition types will be the sabot that keeps the round steady as it travels down the barrel. At least from what we've seen so far, the projectiles themselves will be largely uniform no matter what weapon is firing them.

The Navy has not said when it expects the HVP to transition from a research and development effort into a fully-fledged procurement program or when its destroyers and cruisers might begin carrying the projectiles on actual operational patrols. But the testing at RIMPAC shows that the service is steadily pushing ahead to get this game-changing ammunition ready for action on its Arleigh Burkes and Ticonderogas, as well as other platforms at sea and on land.